Rainbow Day Camp serves a small but fast-growing population: transgender kids, ages 4-12. Experts say the California camp's rapid growth reflects the dramatic increase in children "socially transitioning" at younger ages across the country.

EL CERRITO, Calif. —

Rainbow Day Camp serves a small but fast-growing population: transgender kids, ages 4-12. Experts say the California camp's rapid growth reflects the dramatic increase in children "socially transitioning" at younger ages across the country.